The El Reno Survey Project: Crowd-sourced Database Development, Synchronous Photogrammetric Observations and 3-D Mapping of the Largest Documented Tornado

The El Reno, Oklahoma supercell thunderstorm of 31 May 2013 produced the largest documented tornado (~4.3 km diameter), with internal sub-vortices featuring the second-strongest wind speeds ever documented within a tornado (>135 ms-1). Although the El Reno tornado is notorious for being the first storm to directly cause storm chaser mortalities, the wealth of observational data makes it an exceptional subject for scientific investigation. The tornadic mesocyclone was sampled by multiple remote-sensing platforms, including mobile research and operational radars and lightning detection networks. Post-storm surveys documented the tornado track and associated damage in considerable detail. Additionally, high-resolution imagery and video footage was captured by a multitude of storm chasers within the storm's vicinity. In a modern analog to T.T. Fujita's pioneering effort to analyze multi-perspective imagery of the 1957 Fargo ND tornadoes, our research team is conducting the El Reno Survey (http://el-reno-survey.net/), a project designed to crowd-source storm chasers for imagery and data and compile submitted materials in a quality controlled, open-access research database for use by the scientific community and other interested users.

Internet searches identified at least 250 chase teams that observed and obtained imagery of the El Reno Storm. Solicitations to the storm chaser community for participation in the project, extended via various social media outlets, resulted in responses greatly exceeding initial expectations. As of July 2014, 77 registered participants have contributed their imagery and data resources to the project database for unrestricted research purposes, and others continue to enroll. Participation involves a two-step process, whereby registrants submit an online form providing metadata and a narrative of their chase experience, and then upload video, still images and GPS logs. The project database contains what is likely the largest archive of visual material ever compiled for a single tornado. This data will become accessible to all interested users from the Madison Severe Local Storms meeting onwards through a simple registration process.

This presentation will describe the survey approach and detail methods developed to precisely fix the time and location characteristics of uncontrolled storm chaser imagery to make it usable for scientific purposes. Collation of synchronous multi-perspective imagery also enables the generation of some first-ever three-dimensional products, such as mapping of extremely intense sub-vortices and 3-D animations of important phases of the tornado's evolution. These methodologies employed by our survey are presented as a new model for post-storm data collection, with templates and instructional materials being created to facilitate replication by interested parties for both past and future tornadic storms of special research interest.